Abstract
Ideal Plant Architecture 1 (IPA1) encodes SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 14 (SPL14) with a pleiotropic effect on regulating rice development and biotic stress responses. To investigate the role of IPA1 in early seedling development, we developed a pair of IPA1/ipal-NILs and found that seed germination and early seedling growth were retarded in the ipa1-NIL. Analysis of the soluble sugar content, activity of amylase, and expression of the α-amylase genes revealed that the starch metabolism was weakened in the ipa1-NIL germinating seeds. Additionally, the content of bioactive gibberellin (GA) was significantly lower than that in the IPA1-NIL seeds at 48 h of imbibition. Meanwhile, the expression of GA synthesis-related gene OsGA20ox1 was downregulated, whereas the expression of GA inactivation-related genes was upregulated in ipa1-NIL seeds. In addition, the expression of OsWRKY51 and OsWRKY71 was significantly upregulated in ipa1-NIL seeds. Using transient dual-luciferase and yeast one-hybrid assays, IPA1 was found to directly activate the expression of OsWRKY51 and OsWRKY71, which would interfere with the binding affinity of GA-induced transcription factor OsGAMYB to inhibit the expression of α-amylase genes. In summary, our results suggest that IPA1 negatively regulates seed germination and early seedling growth by interfering with starch metabolism via the GA and WRKY pathways.
Highlights
Seed germination is a complex and diverse process that plays an important role in ensuring the continuity of life
We further investigated the effect of exogenous GA on the seed germination of the near-isogenic lines (NILs) and, as a result, GA3-promoted germination and seedling growth were clearly observed in ipa1-NIL seeds (Figure 3C–G), previous studies have reported that the exogenous GA application has little effect on the germination of the miR156 mutant or Ideal Plant Architecture 1 (IPA1)-OE seeds [18,22]
For the GA synthesis-related genes, our results demonstrated that OsGA20ox1 was markedly downregulated in the ipa1-NIL seeds during germination (Figure 4C)
Summary
Seed germination is a complex and diverse process that plays an important role in ensuring the continuity of life. Our work suggests that the elevated levels of IPA1 expression retards seed germination and early seedling growth through GA and WRKY pathways. Sci. 2021, 9226, 6h60g5erminated on filter paper soaked with GA3 solution (Figure 3F,G) These data suggest that ipa retards the seed germination and early seedling growth at least via a mechanism mediated by a reduction in the abundance of bioactive GAs. Bioactive gibberellins are regulated by changes in biosynthetic and deactivation pro2.4. RAmy3B/C, RAmy3D, and RAmy3E, especially RAmy3D, were upregulated quickly, which might be induced by sugar starvation as reported in the previous studies [24,25] These observations suggested that IPA1 negatively regulates the early seedling development of rice by interfering with starch metabolism via the GA pathway. Our results suggested that IPA1 retards seed germination and early seedling growth by interfering with starch metabolism via both the GA and WRKY pathways
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